In the liquid processing industry, such as the food, beverage, pharmaceutical and biotechnology industry, processing devices such as emulsifiers, homogenisers and mixers have been used for many years in certain steps of the production process. They are often intended for shearing of the products. The purpose of such shearing is above all to shear product clusters and/or materials into smaller particles and disperse them in a more or less liquid product bulk. The purpose can also be to mix more or less liquid products with each other that are difficult to mix, for instance oil-based liquid with water-based liquid.
A common feature of processing devices of the above type is that their processing unit is positioned and operates inside the process vessel whereas the drive for driving it is positioned outside the vessel. The driving force is transmitted by a drive shaft usually made of metal, which extends through the wall of the vessel, either from the top or from the bottom thereof. In both cases, the drive shaft must be sealed with rotary seals to prevent leakage between the surroundings of the vessel and the enclosure formed by the vessel.
There is a constant and well-known problem with this type of rotary seals in the sense that they are constantly exposed to wear, which results in particle generation, and without previous warning start to leak during the process. In most cases this leakage results in microbial and/or particulate contamination of the products that are being processed and, thus, causes in most cases a total loss of the entire product batch.
A further problem of prior-art processing devices is that they have hidden cavities in the stuffing boxes and have long drive shaft supports, which practically cannot be cleaned in situ. In many applications, especially in the pharmaceutical and biotechnology industry, this problem can be disastrous if it is not taken care of. The problem may cause cross-contamination of various infected products between the batches. In most cases this results in loss of the batch.